The disclosure relates in general to refueling aircraft and more specifically to methods and apparatus for resisting torsional loads in aerial refueling booms.
Aircraft in flight are commonly refueled from a refueling aircraft. The refueling aircraft is typically provided with a telescopic boom mechanism or a flexible hose which trails behind the refueling aircraft and physically makes a connection to the aircraft to be refueled (i.e., the receiver aircraft).
Refueling aircraft have a plurality of wing fuel tanks and a central wing tank. Auxiliary fuel tanks can also be provided within or proximate to a fuselage of the aircraft. Fuel is commonly transferred to the boom or hose via a single wall header which is isolable by one or more shut-off valves. Common refueling systems include pumps to pressurize the fuel for transfer from one or more of the tanks, and valves which are controlled between an open and closed condition by simple on-off switches normally positioned on a refueling system panel and manually selected by a trained refueling operator.
During an aerial refueling operation utilizing a refueling tanker with a telescopic boom, torsional loads are introduced to the boom by the actions of the receiver aircraft and the aerodynamic loading on the boom. To better understand this phenomenon, it is beneficial to discuss the disadvantages of conventional refueling boom designs. In this regard, reference is made to FIG. 1 in which is shown in cross section a conventional boom 10 including an outer tube 12 and an inner tube 14. The outer tube 12 is a fixed portion of the boom and houses the inner tube 14 which extends in a telescopic manner for the purpose of engaging and refueling a receiver aircraft.
The conventional boom 10 also includes two pairs of rollers: an upper pair of rollers 16a and a lower pair of rollers 16b. The upper rollers 16a and the lower rollers 16b apply counter forces to both vertical and horizontal loads applied to the boom during refueling operations. The presence of vertical and horizontal loads can create torsional loads. While the inclusion of rollers 16 to counteract the vertical and horizontal loads is taken into consideration, conventional booms do not take into consideration these torsional loads. Accordingly, conventional booms may be subject to excessive wear on the rollers 16. In addition, analysis of the wear of the rollers 16 and the inner tube 14 has revealed the presence of torsional loads.
In view of the foregoing, there is a need in the art to overcome the disadvantages of conventional telescopic booms. In addition, there is a need to adequately resist or react to the torsional loads subject on refueling booms. Still further, there is a need to reduce the frequency and length of time required to maintain booms subject to torsional loads.